btrfs: fix iteration of extrefs during log replay

At __inode_add_ref() when processing extrefs, if we jump into the next
label we have an undefined value of victim_name.len, since we haven't
initialized it before we did the goto. This results in an invalid memory
access in the next iteration of the loop since victim_name.len was not
initialized to the length of the name of the current extref.

Fix this by initializing victim_name.len with the current extref's name
length.

Fixes: e43eec8 ("btrfs: use struct qstr instead of name and namelen pairs")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

Author: fdmanana

fs/btrfs/tree-log.c

@@ -1148,13 +1148,13 @@ static inline int __add_inode_ref(struct btrfs_trans_handle *trans,
 			struct fscrypt_str victim_name;
 
 			extref = (struct btrfs_inode_extref *)(base + cur_offset);
+			victim_name.len = btrfs_inode_extref_name_len(leaf, extref);
 
 			if (btrfs_inode_extref_parent(leaf, extref) != parent_objectid)
 				goto next;
 
 			ret = read_alloc_one_name(leaf, &extref->name,
-				 btrfs_inode_extref_name_len(leaf, extref),
-				 &victim_name);
+						  victim_name.len, &victim_name);
 			if (ret)
 				return ret;